Caesarian sections should only take place when they are medically necessary and too many are taking place, according to a stark warning by the World Health Organisation (WHO).

The body has issued its most explicit warning about the impact of the increase in births by the method which has surged in use over the past 25 years.

C-sections in Scotland have been increasing steadily, to more than one quarter (27.8 per cent) of births in for the year to March 2012. It means more than 16,000 babies were born by C-section in that year.

Across the UK, a quarter of children come into the world thanks to the routine procedure compared to around 12 per cent in 1990.

But the WHO has warned the routine procedure can have lasting effects on mothers and babies. One of its leading experts said many western and developing nations, are resorting unnecessarily to the operations.

Other pregnant women with a real medical need for a C-section simply do not have access to the operation, it said.

Marleen Temmerman, director of the WHO's reproductive health department, said: "In a lot of developing and developed countries, there is really an epidemic of Caesarean sections, even when there is no medical need."

The rise is worldwide and thought to be a combination of doctors believing surgery is safer in potentially difficult births and women choosing not to undergo labour.

More than half of women giving birth have caesarean sections in Brazil and the figure rises to over 80 per cent in private hospitals.

However, the procedure carries risks.

However, health experts say the procedure carries risks, and that a baby is more likely to end up in intensive care than if born naturally. Women also stay longer in hospital, have a hysterectomy or a cardiac arrest.

The National Institute of Healthcare and Clinical Excellence (Nice) state that women who want a C-section should be able to have one, even if it is not for medical reasons.

However, in its latest statement, the WHO said the full impact of a C-section on a mother and her child are unclear.

It added: "Across a population, the effects of caesarean section rates on maternal and newborn outcomes such as stillbirths or morbidities like birth asphyxia are still unknown.

"More research on the impact of caesarean sections on women's psychological and social wellbeing is still needed."

There are many countries in the developing world, however, where women and their babies are dying for want of a caesarean section. The WHO says that decisions about whether to operate should be made on a case by case basis, and not according to target figures.

It pointed to Brazil, where some 53 percent of births are by C-section according to WHO figures.

"there is a culture of 'let's go for Caesarean'," Temmerman added.

Since the mid-1980s, doctors have said the ideal rate of C-sections should range between 10 and 15 percent, though the health community is working on establishing a new recommendation.

Ms Temmerman said: "If a country... has a rate that is below 10 percent, you can see that there are more mothers and babies dying because (there is) no access.

"We see women dying" in some countries because they cannot be operated on in time, she added.

According to the WHO's 2008 figures, some 23 percent of births in Europe were by C-section, 35 percent in North and South America, and 24 percent in the Western Pacific.

Only Africa and southeast Asia, with rates of 3.8 and 8.8 percent, appeared to be free from the "epidemic".

Yesterday's recommendations were the first specific call by the WHO to stop childbirth by Caesarean except when it is medically necessary.

"I think this is the first time we are being so explicit about it," said WHO perinatal expert Metin Gulmezoglu.